1. Field of the Invention
This invention relates to a tester for testing microelectronic circuit chips. More specifically, the invention concerns the application of input signals to, and measuring output signals from, a chip under test, and displaying the results of such a test.
2. Brief Descriotion of the Prior Art
Chip testers have been known in the art for more than a decade. Microelectronic chip manufacturers have used sophisticated and complex chip testers in the research and development of new chip types. These testers can check the chip on the master wafer even before individual chips are separated therefrom. A multi-fingered contact assembly may even automatically step and repeat a series of tests on each of a plurality of chips of the master wafer slice.
After scribing and chip separation from the master wafer, the chips are mounted in a multi-pin case and connected to pin terminals by thin wires. After such assembly, the chip may again be tested by contacting the pins of casing and applying input voltages while monitoring output voltages. Again, a series of tests may be applied in order to exercise all possible functions and input conditions.
In the latter type of tester, a more simplified tester is used, but both types of testers described may cost in the tens of thousands of dollars.
Laboratory bench testers are also available for performing measurement testing of microelectronic chips in a laboratory or on the work bench. Such testers will typically have a number of different sockets for accommodating chips having a different number of pins, as well as a number of switches for preliminarily setting up input voltages and output measurements based upon the knowledge of the pin configuration for a particular chip device type. A technician, for example, would look up the device type in a long list of microelectronic chip types, and upon finding the desired chip type in the listing, be given instructions for setting the switches on the tester to predetermined positions so that the inputs of the device under test will have proper levels of voltage and current and so that the output measurement instruments will selectively measure corresponding voltages and/or currents on the output terminals, again for that particular type.
In all of the aforementioned chip testers, the chip type must be known before the testing commences, and the socket for the chip (or the finger probes) must be assigned specific voltages and/or currents for application to the predetermined input pins of the device under test. The output terminals of the device under test must be predetermined so that the measurement of the voltages and/or currents at the output terminals can be compared against prescribed standards. In all cases, the exact position of all input pins, power supply pins, and output pins (or contact pads) for the chip under test are known. If a different chip is to be tested, especially if the second chip has a different pin configuration for input, power, and output terminals, and/or has a different number of pins on the case of the device, the second chip to be tested must be inserted in different socket, and before insertion, the selectable switching arrangement must be manually or automatically rearranged so as to apply input voltages/currents to input terminals, proper power supply voltages to power terminals, and output measurement instruments to output terminals.
For the technician in the laboratory or the work bench of a service department, the testing of a chip can be an extremely time consuming effort. First, it is necessary to identify the nomenclature on the casing to determine the chip type. This is sometimes difficult, especially to a novice, since microelectronic chips are typically encoded with date codes, manufacturer part numbers, patent numbers, and the like, as well as the actual part number to identify the function of the device.
After the technician has determined the correct chip type, he or she locates that chip type in a list of hundreds of chip types and methodically sets a number of switches to the prescribed settings in the listing in order that the chip to be tested will have proper input, power, and output terminal connections. The technician then locates in the listing the proper socket to plug the chip into, and only after such a procedure the chip under test can be evaluated.
It is clear that there is a need in the art for a simplified chip tester that will eliminate or minimize the efforts involved in identifying the chip type, that will automatically insure proper pin contacts for input, power, and output lead connections, and that will perform a repetitive test over a long period of time on the chips for the detection of intermittent malfunctions. The present invention fills this need.